A wide variety of operations, especially food processing, involve the application of a fluid coating material. In particular, the preparation of certain presweetened Ready-To-Eat ("R-T-E") breakfast cereals involves the application of a sticky sugar coating solution or slurry to a prepared R-T-E cereal base. The wet, sugar coated R-T-E cereal is subsequently dried and packaged to form the finished product.
Conventionally, the sugar coating solution or slurry is applied to the R-T-E cereal base with conventional spray nozzles that dispense the slurry in a spray pattern using only the hydrostatic pressure of the slurry supply to form the spray. The nozzles are typically mounted within an R-T-E cereal base enrober. A good description of such coating apparatus and techniques is given in "Breakfast Cereals and How They Are Made" (edited by R. B. Fast and E. F. Caldwell), American Association of Cereal Chemists, Inc., 1990, pg. 200-220. Such an enrober is an apparatus having a rotating horizontally extending vessel or drum, generally cylindrically shaped, although the axis may be at a slight angle relative to the horizontal, frequently having a lower discharge end. The cereal base is fed at one end and is discharged at the opposite end. As the vessel rotates and as the slurry is dispensed within the enrober, the slurry is evenly applied, more or less, as the cereal is tumbled within and travels along the axis of the enrober. While useful and effective, the ease of conventional hydrostatic slurry restrictive orifice discharge nozzles has numerous disadvantages.
One disadvantage involves the gradual build-up of the slurry upon the interior of the enrober vessel. After this build-up of sugar, the enrober must be thoroughly cleaned. Depending upon a variety of factors, the cleaning operation must be conducted at least once per day and perhaps as frequently as once per operating shift. cleaning the enrober is thus a standard element of operating hygiene that usually takes up to an hour to perform. Thus, slurry build-up requires the direct cost of maintenance servicing. More importantly, since most cereal processing lines are generally continuous, slurry build-up can cause the more significant cost of downtime of the entire cereal processing line.
Still another problem with the use of conventional restrictive orifice nozzles involves the evenness of the slurry distribution over the cereal base. Of course, an evenly distributed slurry is desired. Using conventional nozzles, improved evenness of distribution can be obtained by greater tumbling (e.g., faster rotation and/or increased residence time in the enrober). However, many R-T-E cereals, especially those in flake form, are fragile. Greater tumbling leads to the development of broken flakes or fines that subsequently must be screened out. Fines generation can lead to yield losses of up to 5% or more of the cereal line's capacity.
Still another problem is undesirable product agglomeration. Undesirable product agglomeration can be aggravated by poor slurry distribution. Undesirable product agglomeration can result in the generation of large, unattractive, hard pieces that should be screened out.
Still another benefit resides in the reduction in the amount of expensive sugar ingredients lost as part of the sugar build-up that must be washed away during enrober cleaning. Still another advantage resides in reduction in undesirable product agglomerates.
Surprisingly, dramatic improvements in the sugar solution coating of R-T-E cereal has been obtained utilizing an enrober including a drum having a hydrophobic material internal surface, steam assisted slurry nozzles and/or an air atomized, drum spray system. One benefit is a marked decrease in the amount of sugar build-up upon the enrober's interior surface that allows for reductions in cleaning service requirements and its concomitant losses in production capacity.
Still another advantage resides in reduction in undesirable product agglomerates.